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Evaluation of Residue Management in Irrigated RiceEvaluation of Residue Management in Irrigated Rice--based Systemsbased Systems of the Mekong Deltaof the Mekong Delta
Closing Nutrient Cycles by the Use of Organic Substrates from DeClosing Nutrient Cycles by the Use of Organic Substrates from Decentralized Water Managementcentralized Water Management
E. Saleh, M. Becker and F. Asch. Institute for Plant Nutrition, University of Bonn, Germany.N. H. Chiem, D. V. Ni, T. K. Tinh and K. V. Thanh. University of Can Tho, Vietnam.
PITROSwww.pitros.uni-bonn.de
SANSEDwww.sansed.uni-bonn.de
Mungbean response to different organic substrates (3 Mg ha-1)
0 2 4 6 8
Control
Mungbean response to different Biogas Sludge application rates
Ap
plic
atio
n r
ate
(Mg
ha
-1-d
ry m
atte
r)
0 1 2 3 4 5 6
0.0
1.5
3.0
4.5
6.0
7.5
9.0
StoverGrain
Maize
Tomato
Cowpea
Mungbean
Soybean
Cassava
Yam
Sweet potato
0 20 40 60 80 100 120Increase in biomass (% obove unamended control)
Crops response to Biogas Sludgeapplication (3 Mg ha-1)
StoverGrain
Biomass (Mg ha-1)Biomass (Mg ha-1)
Agricultural land use in the Mekong Delta is dominated by intensive irrigated rice double and triple cropping on alluvial and acid sulphate soils.
A generally observed decline in productivity is linked to a low N use efficiency and soil organic matter content on the alluvial soils (An Binh site).
Crop production is constraint by nutrient imbalances such as aluminum toxicity and P deficiencies on the acid sulphate soils (Hoa An site).
Recently, the cultivation of higher-value cash crops in aerobic soil during the dry season has been emerging.
Organic substrates from decentralized waste/water management are widely available but are unlikely to be applied to lowland rice.
However, they may help alleviate the problems of low soil organic matter content and Al toxicity, particularly in the high-value upland crops, grown in rotation with rice.
Background Background Materials and Methods Materials and Methods Geographical location:105�43’40’’ E and 10�00’05’’ N.Monsoon climate, dry season between December and April.
Alluvial soil:Silty clay (57% clay, 34% Silt, 9.0% Sand).pH: 4.9 – 5.1, C org.: 3.7 – 3.9 %, N tot.: 0.14 – 0.17 %. Acid sulphate soil:Silty clay (44% clay, 55% Silt, 1.0 Sand).pH: 3.3 – 3.5, Al3+:37 mg 100g-1, P available: 1.2 – 2.5 mg 100g-1.Laboratory experiments:Anaerobic N mineralization (NH4
+ in amended soils with different substrates) in the dark at 30 – 35 ºC for three weeks. Weekly NH4
+ content was analyzed after KCl extraction by colorimetry. Organic substrates decomposition (weight loss) was determined by weight loss from litter bags after 12 weeks.
Field experiments:1. Comparison of substrates: Unamended control, pig manure – rice straw compost, biogas sludge from cement tank, biogas sludge from plastic tank, biogas compost, champost, rice straw compost, vermicompost from pig manure, vermicompost from goat manure, fish pond residue (1. 3 Mg ha-1). RCBD, 4 Reps, Vigna radiata as test crop.2. Comparison of application rates: Biogas sludge applied at 0, 1.5, 3, 4.5, 6, 7.5, and 9 Mg ha-1. RCBD, 4 Reps, Vigna radiata as test crop. 3. Comparison of test crops: Biogas sludge applied 3 Mg ha-1 . Seven test crops (tubers –yam, cassava, sweet potato; legumes – mungbean, cowpea, soybean; vegetables – tomato, sweet corn.
Pi
g
ma
nu
re
-ri
ce
str
aw compost
Vermicom
post(
Goa
t
man
ur
e)
Vermicom
post(
Pi
g
ma
nu
re
)B
io
ga
s
sl
ud
ge
co
mp
.
2
mo
nt
hs
Bi
og
as
s
lu
dg
e
co
mp
.
6
mo
nt
hs
Ri
ce
st
ra
w
co
mpo
st
Mu
sh
ro
om
c
om
po
st
Bi
og
as
s
lu
dg
e
(c
em
en
t
ta
nk
)
Bi
og
as
s
lu
dg
e
(p
la
st
ic
ta
nk
)
Fi
sh
po
nd
re
si
du
e
Net
Nm
iner
alza
tio
nra
te (
pp
m)
0,0
0,5
1,0
1,5
2,0
2,5Net N mineralization rate (NH4
+-N) in substrate-amended alluvial soil)
Net
wie
gh
tlo
ss (
g)
0,0
0,5
1,0
1,5
2,0
2,5
Decomposition of substrates in an alluvial soil after 12 weeks
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
0,0
0,1
0,2
0,3
0,4
Net
Nm
iner
alza
tio
nra
te (
pp
m) Net N mineralization rate (NH4
+-N) in a substrate-amended acid sulphate soil)
Net
wie
gh
tlo
ss (
g)
Decomposition of substrates in an acid sulphate soil after 12 weeks
Acid Sulphate SoilAcid Sulphate Soil
Mineralization patterns of organic substrates are affected by substrate quality and soil type.
Organic substrates differentially affect crop biomass with biogas sludge showing largest effects.
Mungbean production increased significantly with substrate appli-cation rates.
Cowpea and mungbean respon-ded more to substrate appli-cation than tubers or vegetables.
These results are seen to guide nutrient cycling from decentra-lized waste/wastewater treatment in the Mekong Delta.
Pi
g
ma
nu
re
-ri
ce
s
tr
aw
co
mp
os
t
Ve
rm
ic
om
po
st
(
Goa
t
man
ur
e)
Ve
rm
ic
om
po
st
(
Pi
g
ma
nu
re
)B
io
ga
s
sl
ud
ge
com
p.
2
mo
nt
hs
Bi
og
as
sl
ud
ge
com
p.
6
m
on
th
s
Ri
ce
st
ra
w
com
po
st
Mu
sh
ro
om
c
om
po
st
Bi
og
as
sl
ud
ge
(c
em
en
tt
an
k)
Bi
og
as
sl
ud
ge
(p
la
st
ic
ta
nk
)
Fi
sh
p
on
d
re
si
du
e
N mineralization of substrate-amended soil (upper) and weight loss from litter bags (lower)
Alluvial SoilAlluvial Soil
N mineralization of substrate-amended soil (upper) and weight loss from litter bags (lower)
Pig manure-rice straw compost
Vermicompost(Goat manure)
Vermicompost(Pig manure)
Biogas sludge comp. 2 months
Biogas sludge comp. 6 months
Rice straw compost
Mushroom compost
Biogas sludge (cement tank)
Biogas sludge (plastic tank)
Fish pond residue
